oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 37 )

2018 ( 306 )

2017 ( 329 )

2016 ( 392 )

Custom range...

Search Results: 1 - 10 of 209456 matches for " Alison L Pidoux "
All listed articles are free for downloading (OA Articles)
Page 1 /209456
Display every page Item
Plasticity of Fission Yeast CENP-A Chromatin Driven by Relative Levels of Histone H3 and H4
Araceli G Castillo equal contributor,Barbara G Mellone equal contributor,Janet F Partridge,William Richardson,Georgina L Hamilton,Robin C Allshire ,Alison L Pidoux
PLOS Genetics , 2007, DOI: 10.1371/journal.pgen.0030121
Abstract: The histone H3 variant CENP-A assembles into chromatin exclusively at centromeres. The process of CENP-A chromatin assembly is epigenetically regulated. Fission yeast centromeres are composed of a central kinetochore domain on which CENP-A chromatin is assembled, and this is flanked by heterochromatin. Marker genes are silenced when placed within kinetochore or heterochromatin domains. It is not known if fission yeast CENP-ACnp1 chromatin is confined to specific sequences or whether histone H3 is actively excluded. Here, we show that fission yeast CENP-ACnp1 can assemble on noncentromeric DNA when it is inserted within the central kinetochore domain, suggesting that in fission yeast CENP-ACnp1 chromatin assembly is driven by the context of a sequence rather than the underlying DNA sequence itself. Silencing in the central domain is correlated with the amount of CENP-ACnp1 associated with the marker gene and is also affected by the relative level of histone H3. Our analyses indicate that kinetochore integrity is dependent on maintaining the normal ratio of H3 and H4. Excess H3 competes with CENP-ACnp1 for assembly into central domain chromatin, resulting in less CENP-ACnp1 and other kinetochore proteins at centromeres causing defective kinetochore function, which is manifest as aberrant mitotic chromosome segregation. Alterations in the levels of H3 relative to H4 and CENP-ACnp1 influence the extent of DNA at centromeres that is packaged in CENP-ACnp1 chromatin and the composition of this chromatin. Thus, CENP-ACnp1 chromatin assembly in fission yeast exhibits plasticity with respect to the underlying sequences and is sensitive to the levels of CENP-ACnp1 and other core histones.
Telomeric Repeats Facilitate CENP-ACnp1 Incorporation via Telomere Binding Proteins
Araceli G. Castillo, Alison L. Pidoux, Sandra Catania, Micka?l Durand-Dubief, Eun Shik Choi, Georgina Hamilton, Karl Ekwall, Robin C. Allshire
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069673
Abstract: The histone H3 variant, CENP-A, is normally assembled upon canonical centromeric sequences, but there is no apparent obligate coupling of sequence and assembly, suggesting that centromere location can be epigenetically determined. To explore the tolerances and constraints on CENP-A deposition we investigated whether certain locations are favoured when additional CENP-ACnp1 is present in fission yeast cells. Our analyses show that additional CENP-ACnp1 accumulates within and close to heterochromatic centromeric outer repeats, and over regions adjacent to rDNA and telomeres. The use of minichromosome derivatives with unique DNA sequences internal to chromosome ends shows that telomeres are sufficient to direct CENP-ACnp1 deposition. However, chromosome ends are not required as CENP-ACnp1 deposition also occurs at telomere repeats inserted at an internal locus and correlates with the presence of H3K9 methylation near these repeats. The Ccq1 protein, which is known to bind telomere repeats and recruit telomerase, was found to be required to induce H3K9 methylation and thus promote the incorporation of CENP-ACnp1 near telomere repeats. These analyses demonstrate that at non-centromeric chromosomal locations the presence of heterochromatin influences the sites at which CENP-A is incorporated into chromatin and, thus, potentially the location of centromeres.
Factors That Promote H3 Chromatin Integrity during Transcription Prevent Promiscuous Deposition of CENP-ACnp1 in Fission Yeast
Eun Shik Choi,Annelie Str?lfors,Sandra Catania,Araceli G. Castillo,J. Peter Svensson,Alison L. Pidoux,Karl Ekwall,Robin C. Allshire
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002985
Abstract: Specialized chromatin containing CENP-A nucleosomes instead of H3 nucleosomes is found at all centromeres. However, the mechanisms that specify the locations at which CENP-A chromatin is assembled remain elusive in organisms with regional, epigenetically regulated centromeres. It is known that normal centromeric DNA is transcribed in several systems including the fission yeast, Schizosaccharomyces pombe. Here, we show that factors which preserve stable histone H3 chromatin during transcription also play a role in preventing promiscuous CENP-ACnp1 deposition in fission yeast. Mutations in the histone chaperone FACT impair the maintenance of H3 chromatin on transcribed regions and promote widespread CENP-ACnp1 incorporation at non-centromeric sites. FACT has little or no effect on CENP-ACnp1 assembly at endogenous centromeres where CENP-ACnp1 is normally assembled. In contrast, Clr6 complex II (Clr6-CII; equivalent to Rpd3S) histone deacetylase function has a more subtle impact on the stability of transcribed H3 chromatin and acts to prevent the ectopic accumulation of CENP-ACnp1 at specific loci, including subtelomeric regions, where CENP-ACnp1 is preferentially assembled. Moreover, defective Clr6-CII function allows the de novo assembly of CENP-ACnp1 chromatin on centromeric DNA, bypassing the normal requirement for heterochromatin. Thus, our analyses show that alterations in the process of chromatin assembly during transcription can destabilize H3 nucleosomes and thereby allow CENP-ACnp1 to assemble in its place. We propose that normal centromeres provide a specific chromatin context that limits reassembly of H3 chromatin during transcription and thereby promotes the establishment of CENP-ACnp1 chromatin and associated kinetochores. These findings have important implications for genetic and epigenetic processes involved in centromere specification.
A DNA Polymerase α Accessory Protein, Mcl1, Is Required for Propagation of Centromere Structures in Fission Yeast
Toyoaki Natsume, Yasuhiro Tsutsui, Takashi Sutani, Elaine M. Dunleavy, Alison L. Pidoux, Hiroshi Iwasaki, Katsuhiko Shirahige, Robin C. Allshire, Fumiaki Yamao
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0002221
Abstract: Specialized chromatin exists at centromeres and must be precisely transmitted during DNA replication. The mechanisms involved in the propagation of these structures remain elusive. Fission yeast centromeres are composed of two chromatin domains: the central CENP-ACnp1 kinetochore domain and flanking heterochromatin domains. Here we show that fission yeast Mcl1, a DNA polymerase α (Polα) accessory protein, is critical for maintenance of centromeric chromatin. In a screen for mutants that alleviate both central domain and outer repeat silencing, we isolated several cos mutants, of which cos1 is allelic to mcl1. The mcl1-101 mutation causes reduced CENP-ACnp1 in the central domain and an aberrant increase in histone acetylation in both domains. These phenotypes are also observed in a mutant of swi7+, which encodes a catalytic subunit of Polα. Mcl1 forms S-phase-specific nuclear foci, which colocalize with those of PCNA and Polα. These results suggest that Mcl1 and Polα are required for propagation of centromere chromatin structures during DNA replication.
Una revisión de la genética del autismo
Alison Mcinnes,L.;
Revista de la Asociación Espa?ola de Neuropsiquiatría , 2002, DOI: 10.4321/S0211-57352002000400002
Abstract: autism is a severe, neurodevelopmental disorder characterized by impairment in social interaction and communication, and by restricted, repetitive and obsessive patterns of behavior. the disorder affects males more fredquently than females and autistic subjects frequently exhibit reduced i.q.s. recent estimates of the prevalence of autism in california show that it is increasing. investigators are looking into the possible genetic and environmental causes of autism. as the disorder is the most heritable psychiatric illness, investigators are making progress isolating susceptibility genes although no environmental factors predisposing to autism have yet been definitely confirmed. in this review i will discuss recent epidemiological findings and the results of current genetic studies.
PCB concentrations in sediments from the Gulf of Nicoya estuary, Pacific coast of Costa Rica
Spongberg,Alison L;
Revista de Biología Tropical , 2004,
Abstract: thirty-one sediment samples collected from 1996-2003 from the gulf of nicoya estuary on the north- western coast of costa rica, have been obtained for pcb analyses. this is part of the first study to evaluate the pcb contamination in coastal costa rica.overall, the concentrations are low, especially when compared to sediments from more temperate climates and/or sediments from more heavily industrialized areas. values average less than 3 ng/g dw sediment, however, a few samples contained up to 7 ng/g dw sediment. sediments with the highest concentrations were located in the punta morales area, where muds were sampled from among mangrove roots. the puntarenas samples had surprisingly low pcb concentrations, likely due to their sandy lithology. the congener distribution within the majority of the samples showed signs of either recent sources or lack of degradation. however, a few sites, specifically some of the inter-gulf islands and more remote samples had congener distributions indicative of airborne contaminants and/or degradation. considering the presence of air-borne pcbs in the gulf of papagayo to the north, the lack of airborne pcbs and more varied congener distribution in the gulf of nicoya estuary was surprising
Coral recruitment patterns in the Florida Keys
Moulding,Alison L;
Revista de Biología Tropical , 2005,
Abstract: this study examines scleractinian zooxanthellate coral recruitment patterns in the florida keys to determine if differences in density or community composition exist between regions.from july to september 2002,nine patch reefs,three in each of the upper,middle and lower keys,were surveyed for coral recruits (colonies <5 cm in diameter)using randomly placed quadrats and transects.coral recruits were enumerated, measured,and identified to genus.fourteen genera of corals were observed across all sites and ranged from five to 13 per site.densities ranged from 6.29 ±1.92 (mean ±se)to 39.08 ±4.53 recruits m -2 ,and there were significant site and regional differences in recruit densities. the density of recruits in the upper keys was significantly lower than in the middle and lower keys.in addition,the upper keys were less diverse and had a different recruit size-frequency distribution.the majority of recruits were non-massive scleractinian species that contribute relatively little to overall reef-building processes,a finding that is similar to previous studies. fewer recruits of massive species were found in the upper keys compared to the middle and lower keys.the recruitment patterns of the reefs in the upper keys could potentially hinder their ability to recover from stress and disturbances.
PCB contamination in marine sediments from Golfo Dulce, Pacific coast of Costa Rica
Spongberg,Alison L;
Revista de Biología Tropical , 2004,
Abstract: twenty-nine marine sediment samples collected from 1996 through 2002 from the golfo dulce embayment of costa rica were analyzed for pcb concentrations. the esquinas river and rincon bay in the northern and western part of the gulf had relatively low overall concentrations of pcbs, with no samples having greater than 2.1 μg/g dw sediment. the port of golfito had the highest overall concentrations, ranging up to 15.7 μg/g dw sediment. these samples were also dominated by higher chlorinated congeners. samples from the deeper (>100m) waters in the northern part of the gulf, as well as within the sediment plume from the rio coto colorado had intermediate values. within the rio coto colorado sediment plume the concentrations did decrease with increasing depth and the congeners showed a shift towards less chlorinated congeners with depth. however, the deep northern basin had some of the highest pcb concentrations and the shift towards less chlorinated congeners was not apparent or significant. whether the anoxic conditions that exist in the deep waters are capable of initiating dechlorination is still unknown. overall, the data from golfo dulce show moderate pcb contamination, despite the pristine nature of the gulf and surrounding lands
PCB contamination in surface sediments in the coastal waters of Costa Rica
Spongberg,Alison L;
Revista de Biología Tropical , 2004,
Abstract: this paper describes the initial investigation of pcb concentrations in four geographical regions (three on the pacific and one in the caribbean) of coastal costa rica: bahia culebra, golfo dulce, golfo de nicoya, and limón. overall total concentrations of pcb were low in all areas except around the port of golfito (golfo dulce). overall average concentration is 2.80 ng/g dw, with a standard deviation of 2.75. the low concentration could be due to lack of contamination or the subsequent degradation in the warm climate, or the low sorptive capacity of the sediment. further investigation is ongoing
PCB contamination in marine sediments from Golfo Dulce, Pacific coast of Costa Rica
Alison L Spongberg
Revista de Biología Tropical , 2004,
Abstract: Twenty-nine marine sediment samples collected from 1996 through 2002 from the Golfo Dulce embayment of Costa Rica were analyzed for PCB concentrations. The Esquinas River and Rincon Bay in the northern and western part of the gulf had relatively low overall concentrations of PCBs, with no samples having greater than 2.1 μg/g dw sediment. The Port of Golfito had the highest overall concentrations, ranging up to 15.7 μg/g dw sediment. These samples were also dominated by higher chlorinated congeners. Samples from the deeper (>100m) waters in the northern part of the gulf, as well as within the sediment plume from the Rio Coto Colorado had intermediate values. Within the Rio Coto Colorado sediment plume the concentrations did decrease with increasing depth and the congeners showed a shift towards less chlorinated congeners with depth. However, the deep northern basin had some of the highest PCB concentrations and the shift towards less chlorinated congeners was not apparent or significant. Whether the anoxic conditions that exist in the deep waters are capable of initiating dechlorination is still unknown. Overall, the data from Golfo Dulce show moderate PCB contamination, despite the pristine nature of the gulf and surrounding lands Un total de 29 muestras de sedimentos recolectadas de 1996 a 2002 en el Golfo Dulce, Costa Rica fueron analizadas determinar las concentraciones de bifenilos policlorinados (PCBs). La Bahía de Rincón y el Río Esquinas en la parte noroeste del Golfo tienen concentraciones relativamente bajas de PCBs, con ninguna muestras superando los 2.1 ug/ dw (peso seco) de sedimento. El puerto de Golfito tuvo las mayores concentraciones hasta un máximo de 15.7 ug/g dw de sedimento. Estas muestras también estuvieron dominadas por los congéneres más clorinados. Las muestras de los sedimentos profundos (>100 m ) de las aguas de la parte norte del Golfo, así como las de la estela del Río Coto Colorado, tienen concentraciones intermedias. Dentro de la estela de sedimentos del Río Colorado las concentraciones aumentaron con la profundidad y los congéneres variaron con la profundidad hacia los menos clorinados. Sin embargo, la región profunda tuvo una de las más altas concentraciones de PCBs, pero la tendencia hacia los menos clorinados no fue aparente o significativa. No se conoce si las condiciones anóxicas en las aguas profundas son capaces de iniciar la declorización. En general, las muestras analizadas muestran concentraciones moderadas de PCBs, no obstante las condiciones pristinas del Golfo y su cuenca
Page 1 /209456
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.